This invention relates to spatial measurement devices and to coordinate grid patterns used as reference in connection with certain types of spatial measurement, and more particularly to reference point arrays used in connection with swiveling, coordinate measuring arms of the type disclosed in my U.S. Pat. No. 5,829,148 issued Nov. 3, 1998, which patent is incorporated by reference in this specification.
A swiveling, spatial coordinate measuring arm has a limited reach in any direction of typically 1,500 mm, When taking measurements upon a large work piece such as an automobile, the arm must be moved to an number of locations. These locations must be precisely identified in reference to a large, volumetric coordinate system having a singular origin, also known as a global coordinate system. One of the most common and most practical methods of achieving global measurements with an articulated arm of limited reach is to define the location of the arm in relation to three known points in a surrounding reference grid or matrix. Each reference point on the grid or matrix carries a unique identification. Every time the operator moves the arm to a new location, the tip of the arm probe is successively positioned upon three identified points on the grid or matrix, each time the operator manually enters into the associated data processing system the unique identification of each reference point, the data processing system uses the three measurements to calculate the exact position in the arm. The coordinates of that position are then taken into account when determining the result of future measurements in reference to the global coordinate system. The manual entry by an operator of the three reference point identifications is not only time consuming, but is subject to human errors. Indeed, in a work environment, the labeling of a reference point identification may be difficult to read due to poor lighting conditions or obstruction by dust or debris. A single digit error in manipulating an entry keypad or keyboard can yield erroneous measurements.
This invention results from an attempt to eliminate the above-described weakness in the use of a swiveling spatial coordinate measuring arm or other similar spatial measuring devices on large work pieces.
The principal and secondary objects of the instant invention are to optimize the use of a swiveling, spatial coordinate measuring arm or similar spatial measurement device having a limited reach when making measurements over a large work piece that requires relocation of the measuring instrument, by providing a reference grid or matrix pattern whereby the displacement or relocation of the measuring instrument is automatically loaded into the associated data processing system through a simple maneuver which does not require any kind of human operation subject to human error; and to provide a new type of spatial reference pattern for use in these and other types of spatial measurements.
These and other valuable objects are achieved by laying out over the entire workplace, reference points in a distorted pattern of row and columns in which any triangle defined by joining three closely located reference points is unlike any other such triangle found anywhere else within the overall pattern. Consequently, in order to precisely determine the exact position of a measuring device after its relocation within the work space, it suffices to measure the positions of three closely spaced reference points. From the results of those three measurements, the associated data processing system can easily calculate the exact situs where the measuring device is positioned within a global coordinate system and offset all measurements accordingly.